The present invention relates to a finely-divided powder spray apparatus for discharging finely-divided powders together with a gas flow onto a member to be sprayed such as a substrate by inclining a spray nozzle pipe.
A spacer spray apparatus is known as a representative example of finely-divided powder spray apparatuses, the apparatus uniformly spraying a prescribed amount of spacers for liquid crystal displays (spacer beads) as the finely-divided powders having a uniform particle size between substrates constituting a liquid crystal display panel for liquid crystal display devices, for example, between a glass substrate and a glass or plastic substrate so that the spacers are formed into a single layer.
In the liquid crystal display panel of a liquid crystal display device and the like, particles (spacer beads such as plastic particles and silica particles) having a uniform particle size of about several microns to several tens of microns are sprayed or coated as spacers as uniformly as possible in an amount of 10 to 2000 particles per unit area of 1 mm2 to form a single layer between substrates, for example, between glass substrates, between plastic (organic glass, etc.) substrates other than the glass substrates, and between the plastic substrate and the glass substrate, (hereinafter the glass substrate will be described as a representative example and the aforementioned member to be sprayed are simply referred to as the glass substrate as a whole) so that the space to charge liquid crystals is formed.
Some conventional spacer spray apparatuses spray spacer particles onto the glass substrate by transporting the fine spacer particles together with a gas flow of air, nitrogen, etc., through a thin pipe (transportation pipe) and discharging the particles from a swinging spray nozzle pipe together with the gas stream. The spacer particles are finely-divided powders having a size of several microns to several tens of microns, and liable to float. They are various types of plastic particles or silica particles, and liable to be charged. Therefore, it is difficult to spray the spacers onto the glass substrate at a prescribed density with excellent repeatability. These apparatuses can charge the spacer particles in accordance with a charged polarity (electrostatic polarity) and ground the glass substrate and a table so as to reliably spray the spacer particles onto the glass substrate at the prescribed density.
Recently, the size of a liquid crystal display panel has been increased gradually and a plurality of liquid crystal display panels have often been made of a single glass substrate, and it is therefore required to spray the spacers in a wider area. Thus, an increased swing angle has been required for the spray nozzle pipe to spray the spacers. Accordingly, a distance from the tip of the spray nozzle pipe to the substrate at the center of the substrate is increasingly different from that at the ends of the substrate, and it is difficult to uniformly spray the spacers onto the larger glass substrate.
An object of the present invention is to provide a finely-divided powder spray apparatus, which can uniformly spray finely-divided powders such as spacers onto a member to be sprayed such as a large glass substrate.
The finely-divided powder spray apparatus of the present invention having a spray nozzle pipe for discharging finely-divided powders from the tip onto a member to be sprayed together with a gas stream, which is disposed at a prescribed distance from the member to be sprayed and inclined in a prescribed direction; and
a moving-speed control means which controls a moving-speed of the tip of the spray nozzle pipe based on a density distribution of the finely-divided powders deposited on the member to be sprayed in a trial spray.
In the finely-divided powder spray apparatus of the present invention, the density distribution is represented by a quadratic function which indicates a reduction rate of a density of the deposited finely-divided powders, based on a distance between a peak point in the trial spray and a spray point at which an extension from the spray nozzle pipe intersects with the member to be sprayed.
Further, in the finely-divided powder spray apparatus of the present invention, the quadratic function is composed of a X-axis quadratic function, which indicates a reduction rate of the density of the deposited finely-divided powders based on the distance between the peak point on the X-axis and the spray point, and a Y-axis quadratic function, which indicates a reduction rate of the density of the deposited finely-divided powders based on the distance between the peak point on the Y-axis and the spray point.
Further, in the finely-divided powder spray apparatus of the present invention, a moving-speed of the tip of the spray nozzle pipe is decreased under control as the reduction rate of the density of the deposited finely-divided powders is increased.
According to the finely-divided powder spray apparatus of the present invention, the moving-speed of the tip of the spray nozzle pipe is lowered under control by a moving-speed control means in accordance with the quadratic function, which indicates the reduction rate of the density of the deposited finely-divided powders based on the distance between the peak point in the trial spray and the spray point, as the reduction rate of the density of the sprayed finely-divided powder is increased, whereby the finely-divided powders may be uniformly sprayed on the larger member to be sprayed.